Method of making a waterproof gas-permeable plastic sheet



Oct. 24, 1967 J. J. ABELL ETAL METHOD OF MAKING A WATERPROOF GAS-PERMEABLE PLASTIC SHEET Original Filed Dec. 20, 1962 WATER PEPELLENT INTO THE RES/N GEANUL ES STE/ 2 SPFEHD RES/N GRAN U L E5 o/v F/PEOUS SHEET 400 F/BR'OUS SHEET OVER RES/N GK/INULES H547 0ND PRESSURE SUFFICIENT 7U SINTEE RES/N GKI NULES W4 TEE/ ROM, M/CAOPOEOUS PER/45451.5 PLHSTIC SHE E T F/BFOUS SHEE T FIBFOUS SHEET 1N VEN TORS JTFRROLD J. :4BELL BY PIC/MRO C. BERRY United States Patent This application is a division of Serial No. 245,998, filed December 20, 1962, now US. Patent No. 3,262,834.

The present invention relates to a porous plastic structure and more particularly a plastic material which is very permeable to gases, such as, air and water vapor but which is also waterproof. The material of the present invention may be in the form of a self-supporting sheet, or it may be laminated to one or more layers of gas permeable sheet material.

It is well known that plastic sheets are generally waterproof. However, the waterproof plastic sheets of the prior art have a low degree of permeability to air or water vapor. In uses for such sheets where human comfort is a factor, such as, garments and all types of upholstery, air and water vapor are trapped between the plastic and the wearer causing considerable discomfort.

Plastic sheet materials have been made which are porous and gas-permeable, but these materials are not highly water repellent. Efforts have been made to waterproof such porous materials without drastically reducing their gas permeability by treating the surface of the material. However, the compounds used in such treatment wear off with use, and the material quickly loses its water repellency.

It is, accordingly, an object of the present invention to provide a porous plastic structure which is very permeable to gases, such as air and water vapor, but which is also waterproof.

Another object of the present invention is to provide a waterproof gas-permeable plastic sheet suitable for use in garments either by itself or as a layer of a composite material.

A further object of the present invention is to provide a waterproof, gas-permeable plastic structure wherein the agent or agents which impart waterproofness are incorporated throughout the structure and are, therefore, not lost with use.

Additional objects and advantages of the present invention will be apparent from the following detailed description thereof:

In Yarrison, application Serial No. 829,443, filed July 24, 1959, now Patent No. 3,067,469, and in Berry et al., application Serial No. 221,555, filed September 5, 1962, now US. Patent No. 3,258,513, there are disclosed methods of making microporous structures which are gaspermeable. In accordance with the Yarrison application, granules of thermoplastic resin are distributed as a uniform layer on a resilient fibrous sheet. A second resilient fibrous sheet is then placed on top of the resin granules, and the assembly is passed between hot plates defining a passage of diminishing thickness to compress the assembly and sinter the resin particles. As a result of this treatment, the resin particles are formed into a strong uniformly sintered sheet. The Berry et al. application comprises an improvement over the Yarrison application and discloses a method of applying various surface treatments to a sintered plastic material during its manufacture including either mechanically bonding a fabric to the sintered sheet and/or applying an embossed surface to the sheet during its manufacture.

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While the porous permeable materials produced in the manner set for in the above mentioned Yarrison application, Serial No. 829,443, and Berry et al. application, Serial No. 221,555, are highly useful in making garments, these materials do not possess any great degree of water repellency. According to the present invention it has been discovered that the resin particles may be formulated so as to give, after sintering, a microporous sheet which, in addition to being gas-permeable, possesses not only a high degree of water repellency but is also waterproof.

In previously mentioned copending applications, the materials used were in the form of thermoplastic granules which could be blended with plasticizers, fillers, pigments, dyes and the like. According to the present invention a Waterproofing system compatible with the resin to be used is mixed with a plasticizer and then this mixture may be blended with the thermoplastic granules in a very fast agitator which generates heat during the blending operation. This blending procedure enables the plasticizer to soak into the resin carrying the waterproofing system components along with it. Good results have been obtained when the compositions to be blended contain 30 to 100 parts by weight of plasticizer per hundred parts by Weight. of resin and 1.0 to 4.0 parts by weight of water repellents per hundred parts by weight of resin. The composition may also include stabilizers, fillers, pigments and dyes, as desired. Other techniques for dry compounding of thermoplastic resins may be used alternatively.

Suitable thermoplastic materials include vinyl resins and other water-insoluble thermoplastic resins which are either flexible by nature or which can be made flexible by suitable agents. Particularly good results are obtained with vinyl resins including vinyl homopolymers, such as polyvinyl chloride, and vinyl copolymers, such as copolymers of vinyl chloride and vinyl acetate. Copolymers of vinyl chloride and vinyl acetate are preferred for use in the invention. These preferred copolymers will contain from to 97% by weight of vinyl chloride.

The plasticizer may be any plasticizer suitable for use with the selected resin. When a vinyl resin is used suitable plasticizers have been found to include dioctyl phthalate, dioctyl sebacate, N-octyl-N-decyl adipate, N-octyl-N-decyl phthalate, polyester plasticizers and monomeric, epoxyester type plasticizers.

The waterproofing system of the present invention can contain any water repellent compatible with the resin and plasticizers used. Good results have been obtained by using water repellents based on silicones, fiuorocarbons and long chain nitrogen complexes, such as the materials marketed under the name Zelan. Particularly good results are obtained when the waterproofing system used is a mixture of Zelan and a fluorocarbon repellent.

The stabilizers which may be incorporated include barium-cadmium-zinc complexes, such as that marketed under the name 6V6A and epoxy stabilizers, such as that marketed under the name Ferro 900.

The composition contemplated for use in this invention includes the following ingredients mixed in the recited proportions Parts by weight per hundred parts by The gas permeability of the final product may be varied, as disclosed in the aforesaid Yarrison application, by controlling the reduction in thickness of the resin particle layer during the application of heat and pressure.

tional view of the waterproof, microporous permeable sheet that is formed by the process. It will be understood, of course, that either or both of the upper and lower fibrous sheets may be removed, if desired.

The following examples are given only by way of illustration and are not intended to in any way limit the scope of the invention.

EXAMPLE I A dry blend of the following composition was made:

Parts by wt. per hundred parts by wt. of resin Copolymer of polyvinyl chloride (97%) and polyvinyl acetate (3%) 100 Normal octyl normal decyl adipate 52 Normal octyl normal decyl phthalate 22 Monoplex 8-73, monomeric, epoxyester type plasticizer 6 6-V-6A, barium-cadmium-Zinc complex stabilizer 2 Pigment 2 GE. SS 4024, water-repellent, 50% active silicones,

50% solvent 3 The blending was conducted in a high speed agitator and continued until substantially allof the plasticizer had been Worked into the resin carrying the active silicone material along with it, the solvent originally present being evaporated by the heat generated by the agitator. The treated resin particles were then formed into a microporous material by sintering between resilient sheets in the manner disclosed in the above mentioned United States application, Serial No. 829,443, now US. Patent No. 3,067,469.

The resulting microporous sheet material was repellent to water in the liquid state, but had a vapor transmission rate (grams/24 hr./ 100 in. at 100 F. and 95% relative humidity) of 90 as compared to 2.6 for. a similar nonporousvinyl film.

EXAMPLE II A series of microporous sheet materials were prepared following the procedure of Example I, but substituting various water repellents for the silicone based water re pellent (G.E. SS 4024). Treated particles were prepared containing the following eight water repellents:

(1) 2.0 phr. of Zelan S (cationic aqueous dispersion of a water repellent long chain nitrogen complex);

(2) 3.0 phr. of Zelan S;

(3) 2.0 phr. of Zelan S and 2.0 phr. of FC-205 (fluorocarbon water repellent);

(4) 2.0 phr. of Zelan S and 1.5 phr. of FC-205;

(5) 2.0 phr. of Zelan S and 1.0 phr. of FC-205;

(6) 2.0 phr. of Zelan S and 0.5 phr. of FC-ZOS;

(7) 2.0 phr. of Zelan S and 0.25 phr. of FC-205;-and

(8) 2.0 phr. of Zelan S and 0.10 phr. of FC-20S.

As used, phr. is intended to mean parts by weight per hundred parts by weight of resin.

From each formulation of treated resin particles sam ples were prepared having air permeabilities (cu. ft./min./ sq. ft. at AP equals 25 in. of. water) of 3, 5 and 10. Each ofthe samples was tested for waterproofness by the dynamic head test disclosed in ASTM D583-58. The results of these tests are summarized in Table I and they, indicate that an increased water repellency is obtained by using a 4 mixture of the two types of agents and that a water repellent formula of 2 phr. of Zelan S and 1 phr. of the fluorocarbon FC-205 yields a particularly effective water repellent product.

TABLE I Water Repellant in phr. of Air Permeabil- Dynamic ity, cu. ft./min./ Head Test,

sq. it. at A P= Oentimeters Zelan S FC-205 25 in. H20

Comparative static head tests at 50 cm. of water were then run according to the procedure described in ASTM D583-58 between a sample having a water-repellent constituent consisting of 2 phr. of Zelan S and a sample having ,a water-repellent constituent consisting of a mixture of 2 phr. of Zelan S and 1 phr. of the fluorocarbon PC- 205, each sample having an air permeability of 3. As shown in Table 2, the static head test results for the sample containing the water-repellent mixture of Zelan S and FC-205 was over 60 minutes, while the results for the sample in which Zelan S alone was used was only 15 minutes. Resistance of 60 minutes or longer to the 50 cm. static head test is generally accepted as criteria of waterproofness.

It will be apparent that many modifications and variations may be elfected without departing from the scope of.

the novel concepts of the present invention, and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

Having thus described the invention, what is claimed is: 1. A method of manufacturing a waterproof microporous permeable plasticsheet which comprises the steps of:

(a) vigorously agitating a mixture comprised of thermoplastic resin granules, a plasticizer and at least one A compatible water repellent so as to cause said plasticizer to blend with said resin granules and carry with it said water repellent to thereby incorporate said water repellentwithin said resin granules, (b) spreading said resin granules in a uniform layer on a compressible fibrous sheet, (c) laying down on the exposed surface of said layer a second compressible fibrous sheet, and (d) applying heat and pressure to the resulting assembly to sinter the [resin granules into a microporous permeable layer. 2. A process as claimed in claim 1 wherein said ther moplastic resin is a vinyl chloride-vinyl acetate copoly mer.

3. A process as claimed in claim 2 wherein said copolymer contains 90 to 97% by Weight of vinyl chloride.

4. A process as claimed in claim 1 wherein said water repellent is a silicone based water repellent.

5. A process as claimed in claim 1 wherein said water repellent is a mixture of a fluorocarbon and a long chain nitrogen complex.

6. A process as claimed in claim 1 wherein a fibrous sheet is bonded to the granular layer.

7. A method of manufacturing a waterproof microporous permeable plastic sheet which comprises the steps of:

(a) vigorously agitating a mixture comprised of thermoplastic resin granules, 30-100 parts by weight per hundred parts by weight of said thermoplastic granules of a plasticizer for said resin granules and 1-4 parts by weight per hundred parts by Weight of said resin granules of at least one water repellent compatible with said plasticizer, so as to cause said plasticizer to blend with said resin granules and carry with it said water repellent to thereby incorporate said water repellent within said granules,

(b) spreading said resin granules in a uniform layer on a compressible fibrous sheet,

() laying down on the exposed surface of said layer a second compressible fibrous sheet, and

(d) applying heat and pressure to the resulting assembly to sinter the resin granules into a microporous permeable layer.

8. A process as claimed in claim 7 wherein said thermoplastic resin is a vinyl chloride-vinyl acetate copolymer.

9. A process as claimed in claim 8 wherein said copolymer contains to 97% by weight of vinyl chloride.

10. A process as claimed in claim 7 wherein said water repellent is a silicone based water repellent.

11. A process as claimed in claim 7 wherein said water repellent is a mixture of a fluorocarbon and a long chain nitrogen compound.

12. A process as defined in claim 7 wherein a fibrous sheet is bonded to the microporous permeable layer.

References Cited UNITED STATES PATENTS 2,507,200 5/1950 Elliott et a1. 117121 2,588,366 3/1952 Dennett 117161 3,004,294 10/ 1961 Richard et al 264127 X 3,067,469 11/ 1962 Yarn'son 264112 3,094,585 6/ 1963 Rudner 264-127 X 3,202,733 8/ 1965 Strauss 264127 X 3,256,121 6/1966 Abell 264126 X 3,258,513 6/1966 Berry et a1 264-112 EARL M. BERGERT, Primary Examiner.

HAROLD ANSHER, Examiner. 

1. A METHOD OF MANUFACTURING A WATERPROOF MICROPOROUS PERMEABLE PLASTIC SHEET WHICH COMPRISES THE STEPS OF: (A) VIGOROUSLY AGITATING A MIXTURE COMPRISED OF THERMOSPLASTIC RESIN GRANULES, A PLASTICIZER AND AT LEAST ONE COMPATIBLE WATER REPELLENT SO AS TOCAUSE SAID PLASTICIZER TO BLEND WITH SAID RESIN GRANULES AND CARRY WITH IT SAID WATER REPELLENT SO AS TO CAUSE SAID PLASTICIZER TO BLEND WITH SAID RESIN GRANULES AND CARRY WITH IT SAID WATER REPELLENT TO THEREBY INCORPORATE SAID WATER REPELLENT WITHIN SAID RESIN GRANULES, (B) SPREADING SAID RESIN GRANULES IN A UNIFORM LAYER ON A COMPRESSIBLE FIBROUS SHEET, (C) LAYING DOWN ON THE EXPOSED SURFACE OF SAID LAYER A SECOND COMPRESSIBLE FIBROUS SHEET, AND (D) APPLYING HEAT AND PRESSURE TO THE RESULTING ASSEMBLY TO SINTER THE RESIN GRANULES INTO A MICROPOROUS PERMEABLE LAYER.
 6. A PROCESS AS CLAIMED IN CLAIM 1 WHEREIN A FIBROUS SHEET IS BONDED TO THE GRANULAR LAYER. 